Adeno-associated virus (AAV) DNA is integrated at same specific site(s) on host cell genome in different AAV carrier clones regardless of AAV type used to initiate carrier state. It has been found that even though the host integration site(s) are specific, the number of copies of AAV DNA integrated vary from clone to clone and are found integrated in a tandem head to tail fashion. Adeno-associated virus (AAV) structural proteins (VP-1, VP-2, and VP-3) contain extensive areas of sequence homology as analyzed by tryptic and chymotryptic mapping. The new data is consistent with previous experiments suggesting that AAV structural polypeptides either arise from a common large precursor protein or from similar transcripts. Preliminary screening of sera and cerebrospinal fluid (CSF) from schizophrenic patients showed no significant differences in the distribution or titer of antibodies to AAV or other parvoviruses.